Generally, heat resistant alloy such as superalloy and titanium have been widely used in various technical fields, for example, military or commercial airplanes, projectiles, liquid rocket engines, automobiles, power generators, medical equipment and petrochemical plant. However, it is very difficult to mechanically process such a heat resistant alloy, for example, cutting, forging, rolling, and extruding. Furthermore, it is also difficult to cast the heat resistant alloy due to the high melting point thereof which is much higher than typical metal. For example, the cutting operation of the heat resistant alloy is very difficult and expense process. A cutting tool is easily damaged if it is used to cut the heat resistant alloy. Therefore, the life time of the cutting tool is seriously reduced after cutting the heat resistant alloy. Also, the metal removal rate thereof is very low. Therefore, the heat resistant alloy is generally cut through a waterjet machine or an electric discharge machine (EDM). After cutting the heat resistant alloy, some post processes are required. While performing the post processes, a great amount of heat resistant alloy is wasted.
In order to overcome such problems for mechanically processing the heat resistant alloy, a processing method using superplastic characteristics shown in a specific condition was introduced. However, the application fields of the processing method using the superplastic characteristics are limited to process a thin sheet metal (thin sheet diffusion bonding). Therefore, there is a demand for a new method for manufacturing a thick complicate shaped structural part made of heat resistant alloy with minimum mechanical processes and minimum post-processes (massive diffusion bonding).
The present invention relates to a method of manufacturing a complicate shaped structural part through diffusion bonding in solid state without using secondary materials after stacking multi-sheet metal. As a related art, a brazing method and a transited liquid phase diffusion bonding method were generally utilized. The brazing method is a method of bonding two materials. In the brazing method, an alloy having a comparatively lower melting point is interposed between target alloys to bond, and a predetermined heat is applied to melt the interposed alloy without melting the target alloys so as to bond the target alloys each other. The transient liquid phase diffusion bonding method uses a diffusion bonding method as well as the brazing method. In the transient liquid phase diffusion bonding method, a liquid phase is temporally formed after brazing, and diffusion bonding is made while sustaining a coupling temperature so as to form isothermal solidification to bond target alloys.
However, these conventional bonding methods use the secondary materials and the activator materials in the middle of bonding interfaces. Furthermore, since the liquid phase is formed in the middle of bonding process, the physical characteristics of the bonding surface may differ from that of the work piece. So, the mechanical strength is deteriorated.